The present invention relates to ramp control systems, and more specifically, but not exclusively, relates to a ramp control system configured to detect obstructions during deployment of a ramp.
Wheelchair ramps provide access for persons in wheelchairs to vehicles such as vans, busses, and other modes of transportation. Wheelchair ramps for vehicles can be deployed by using a variety of controls including interior controls, switches incorporated into locks, and remote controls. In order to prevent a person from being crushed or injured during deployment and stowing of the ramp, typical wheelchair control systems require an operator to constantly push the control button during ramp operation. This requirement that the operator actively hold down the control button during ramp operation creates a number of problems. The operator may have difficulty with constantly pressing the control button due to fatigue. There is also an inconvenience and waste of time to the operator since the operator""s attention must be directed to the ramp. Further, with remote control systems, radio interference can halt the deployment/stowing cycle of the ramp.
Another difficulty faced by wheelchair ramp manufacturers is integrating their wheelchair ramp deployment systems with the pre-existing, standard control systems in vehicles, which are typically installed by the original equipment manufacturer (OEM). These OEM control systems are used control vehicle functions, such as operating locks, windows and sliding van doors. In the past, the ramp deployment system is not integrated with the OEM control system such that each operates independently from one another. Since the two systems do not communicate with one another, one-touch (automatic) control of the ramp is practically impossible. For example, by not knowing whether the door is open, the ramp deployment system can not safely deploy the ramp. To solve this dilemma, the ramp system is configured such that human supervision is required to monitor the operational status of the door and the ramp. In order to deploy and stow the ramp, two separate remote controls are typically used, one for operating the locks and/or doors, which is usually OEM supplied, and a separate one for controlling the ramp deployment system, which is supplied by the ramp system manufacturer. The human operator must first use the OEM supplied remote to unlock and open the vehicle""s door. Once the door is fully open, the operator can then initiate ramp deployment with the ramp system""s remote control. As should be appreciated, using the two separate controls to operate the ramp can be rather cumbersome.
Safety is always a concern when designing systems for deploying wheelchair ramps from vehicles. Without proper safety controls, serious injuries can result from operating such systems. For example, during closure of a vehicle door, an arm or some other extremity can be crushed between the door and the vehicle""s body. To avoid such accidents, some automatic van-door closing systems, which are not specifically designed for use with wheelchair ramp systems, are equipped with obstruction detection systems. In one such obstruction detection system, a tape switch sensor is positioned along the edge of the door in order to sense when an obstruction is blocking door travel. However, tape switches are typically expensive and due to their location are prone to damage.
Another type of system detects obstructions by monitoring door motor current during operation. An obstruction is detected when the current supplied to the door motor exceeds a maximum value. Typically though, as the door components wear overtime friction tends to increase which in turn increases the amount of current drawn by the motor during door movement. This increase in current drawn by the motor can cause the obstruction system to detect obstructions when none are present. Although typical current sensing systems adequately detect obstructions through most of the door""s travel, such systems have difficulty in detecting obstructions when the door is near closure, where obstruction detection is critically needed.
To make access to the vehicle easier, ramp designers try to reduce the slope of a deployed ramp by reducing the ramp""s deployment angle. Some vehicles are equipped with an optional kneeling system that lowers the vehicle so as to reduce the deployment angle. These kneeling systems typically have sensors for determining whether the vehicle is in a standing or kneeling position. However, these sensors can be quite expensive to install and maintain. These sensors are also prone to failure, which can reduce the overall reliability of the kneeling system.
Therefore, there has been a long felt need for a ramp control system that can be operated by a single push or momentary contact of a control device and which has improved safety features.
A wheelchair ramp control system for a vehicle according to the present invention allows for automatic single-touch operation of a wheelchair ramp by having a controller that intercepts communications with an OEM control module, which controls the locks and doors of the vehicle. By intercepting these communications, the ramp controller coordinates and synchronizes ramp deployment and stowing operations with the OEM control module. In one embodiment, the controller utilizes its own obstruction detection system to detect door obstructions. In another embodiment, the OEM control module is used to detect door obstructions.
Further objects, features, advantages, and aspects of the present invention shall become apparent from the detailed drawings and description contained herein.